Field of the Invention
The present invention relates to a coil component, and particularly to a coil component that includes a metal wire containing copper (Cu) and a terminal electrode containing nickel (Ni) and tin (Sn). Moreover, the present invention relates to a terminal component that is used as a terminal electrode of such a coil component.
Description of Related Art
In recent years, small coil components that can be surface-mounted have been frequently used in various electronic devices. Coil components of this kind include a metal wire that is wound around a base, and an end portion of the metal wire is connected to a terminal electrode.
As the terminal electrode, a terminal fitting that has a tin plating on a nickel plating may be used as disclosed in Japanese Patent Application Laid-open No. 2009-158777. The nickel plating prevents a base material of the terminal fitting that is made of copper from coming in contact with the tin plating. The tin plating ensures the wettability of solder at the time of mounting.
As a method of bonding a metal wire on the terminal fitting, as disclosed in Japanese Patent Application Laid-open No. 2003-22916, a thermocompression bonding method is widely used. With the thermocompression bonding method, a CuNi alloy may be formed in the wire connection portion when the metal wire is made of copper. As a result, the terminal fitting and the metal wire are firmly bonded together.
However, if the wire connection portion of the terminal fitting contains a large amount of tin, a Cu—Sn alloy can be easily formed. Depending on the component proportion ratio thereof, the alloy may be melted by heat during reflow or any other process, for example. In some cases, the metal wire could drop off from the wire connection portion.
Such a problem would similarly arise not only when the base material of the terminal fitting is made of metal material but also when the base material of the terminal fitting is made of resin. Furthermore, such a problem could similarly arise not only when the terminal fitting is used but also when a terminal electrode that is formed by plating on a surface of a base of a coil component is used.